Plaster and method of plastering



CROSS REFEREiC tXAlVHNtK R.|.. DlcKl-:Y Erm. 2,556,031

PLASTER AND METHOD 0F PLASTERING June 5, 1951 Original Filed April 2l, 1942 3 Sheets-Sheet 2 Dn E |N.. M m s t e um m 5, n 2 m @uf ,3 G.. Mw. TN... .N m. LL L nn Am E n? LI F EL Yo R mw Y .S mm m m Rm.. mm PL 2 .n mm m; 1a. m. u 1 n 5 n e m .n J o lath to form the retaining keys I3. The troweling is carried out sufficiently to give the plaster a relatively smooth surface and to cause moisture and ne `material to come to the surface so as to form a crust, as mentioned above. The subsequent treatment of the surface can be the same for plaster applied in a single layer as for plaster which has been applied in multiple layers.

The applied plaster can be left with its surface in the relatively smooth condition or can be given further treatment, as will be explained hereinafter. or plain, as represented by the strip or section I4 of Fig. l and as shown also in Fig. 7, our acoustical plaster has somewhat the appearance of conventional lime plaster but, due to characteristics to be later described, possesses a relatively high sound-absorbing and sound-deadening capacity, as well as a relatively high heatinsulating capacity. This smoothly troweled plaster can be painted or otherwise coated to improve its appearance and its ability to be washed or cleaned.

Instead of leaving our plaster with a smooth Vcr plain surface, it can be roughened or stippled `for the purpose of improving its appearance and increasing its sound-absorbing ability. The section or portion l5 of Fig. l represents the plaster after it has been stippled. Figs. 3 and 4 are reproductions of actual photographs of the surface of the stippled plaster, Fig. 3 being normal size" and Fig. 4 being magnified or enlarged ten times. The stippling can be carried out in different ways and with various implements. We prefer to do the stippling in two operations, the rst being executed with a stippling brush or the like and the second being executed with a pronged or nail type stippler. One method of procedure which we have found to be satisfactory is to brush stipple the smoothed plaster promptly after it has been applied to the backing and then nail stippling the plaster after an appropriate intervening drying period which may be 4from sixteen to sixty-four hours depending upon the condition of the plaster. It is desirable that the nail stippling have the effect of breaking the cells in the plaster at the points or areas penetrated by the nails. If the nail stippling is carried out before the plaster has dried sufiiciently, the nails .may have a trowelng effect which produces undesirable crusts or shell-like linings in the holes or passages left by the nails. Figs. 2 and 3 illustrate the surface appear- -ance of the plaster after it has been subjected to the two Vstippling operations just referred to. The brush stippling operation imparts a more or less uniformly distributed pebble-like roughness or texture to the plaster surface, which is produced by the combined penetrating and ^`Amincing action of the bristles ofj the stippling Vbrush. This roughness includes numerous small fand relatively shallow holes or indentations I6 which have been formed by the ends Vof the bristles being poked into the plaster. 'Ihese shallow holes are relatively closely, but somewhat irregularly or haphazardly, spaced and are distributedover'the entire surface.

The nail `stippling may be carried out wit a device having a number of projecting nails or pins spaced about one-half inch apart. 'I'he vnails may be four-penny nails which are on the order of a scant one-sixteenth of an inch in diameter, .but the spacing and size of the nails can be varied if desired. The pointed ends of 4the nails preferably project from the base or When the surface is left smooth- 4 holder a distance somewhat greater than the thickness'of the plaster to be stippled so'that the nails can strike the lath Il and prevent the base or holder of the stippling device from contacting and marking the plaster surface. The nail stippling produces the holes H in the plaster which are the open outer ends of channels or Asbestos of medium length fiber is very satisfacpassages Ha left by the nails and which extend into the plaster a substantial distance inwardly of its surface and preferably to a point at or adjacent the backing or lath Il. One or more of the channels or passages I'Ia can be seen in Fig. 5 which is a photographic reproduction at full or normal scale of a cross-section through our acoustical plaster. One of the passages Ila also appears in the photographic reproduction of Fig. 6 which shows a portion of the same cross-section enlarged ten times. 'The purpose of the open holes I1 and the channels Ila leading inwardly therefrom will be further explained hereinafter.

We will next describe our acoustical plaster composition and explain our method of preparing the plaster. Our acoustical plaster comprises a plastic cementitious material of a creamy consistency formed by mixing water with hydrated lime and then aeratin y xe. Our plaster mosition has oamlng a n incorporated therein which will e furt er identified hereinafter and which makes possible the aeration of the mixture by a mechanica on thereof for the period of time erei'fiitrfspl extend from the front to the rear surfaces thereof and impart to the plaster a porous or a spongy characteristic. These cells serve to entrap and dampen sound waves or vibrations and thus enable the plaster to absorb and deaden sound or noise. These cells also constitute voids which ''enable the plaster to retard the transfer of-heat.

'Instead of using only hydrated lime in forming our acoustical plaster. as above explained, we may add a suitable fibrous material which serves as a ller and re or binder.

tory for this purpose, although other brous materials can be used-such as sisal, ba asse, wood bers, animal hair, or rock wool. The use of suc a HBrous binder is' desirable Because it reinforces the plaster and tends to prevent shrinking or cracking thereof. Some of these fibrous materials, particularly the asbestos, also serve as a plasticizer which holds water and adds to the Aworkability of the plaster.

.The following composition is given as an example of an acoustical plaster which'we have found to be very satisfactory and which comprises the following ingredients in the approximate amounts specified:

The hydrated lime, asbestos.- and the foaming agent maybe premixed in amstate and mags7 be l inthis'oondltion in bags to the job orv construction workwhere the plasterv is. to. be used. At this point the er' may be mixed with water and the mixture may be aerahtled to produce the c lisorbubbles therein. QE it may',- be generally preferable to supply our acoustical plaster composition to the job in a dry stata it1may. in some cases, be desirable` todaliverthe composition tothe job in a. rea -lg wet conditig' y y drated lime may. be a. regular or conventional hydrated lime of the kind used bythe. building trades, or, preferably, may be a finishing grade .of lime such as a. Dolomitic lime having about 92% o! the total ox1des hydrated. In our improved plaster the amount of hydrated lime used is substantially greater than 5013er cent by weight of the solid content as indicatedinthe above-example and, conversely, the amounts of esbestoahcr and foamingl agent used are individually and also. collectively substantially less 50. per cent. by weight of the solid content. The' hydrated lime constitutes the mainA ingredient ofthe composition and the improved plaster can` accordingly beV defined: as. comprising ny." drated limeV in a. major proportion and asbestos ber and foaming agent in. a minor proportion. eshould be in a fine condition, prefera bly. web. 13.95% .will pasathrough a 106. mesh Semen and 160% pass througha 30; mesh screen.

stood, of course, that various other mixing, devicescould bel used and that the period of agitation may be variedsomewhat in accorclance4 withv the particular mixing apparatus employed.

Thev acoustical. plaster resulting from the above-described composition and method operations is of a readily workable creamy consistency,- and. after drying has a ensit o ab 1l 2 pounds per cubic foot. ensity value comes. w1 e. range o 4f td 23 pounds perv cubic, foot and this fact may be taken as an indication that ourplaster is a good acoustical laster.. Likewise this density value falls within the range of 18 to 25 pounds per cubic foot which be taken as an indication that our plaster is; also a good workable plaster.

- Theasbmtosdnay be in the form omedillm...

legtmflbgr, as mentioned above, although asbestosof various other ber lengths could' be used.

' We could: also use any one of the other fibrous known commercially asi-Duponol WA and which isa sodium salt of an ahum, more Aspecically a sodium sul hate o techn ca lau l alcohol. THe amount of foaming agent to be used may Ee greater or less than that specified above depending upon the degree of aeration required, thatime of aeration, and the character of aeratinS eqllpment used.

upon the degree of workability and other characteristics desired inthe plastercomposition, the. amount of water to be used may be greater or less than that mentioned in the above v examples The above-described composition is aerated by mechanical mixing or agitation as indicated above. For t 1s purpose e composition may be mixed or beaten for a period of two tol fifteen minugrafr which it will usually t plastic mass hasrincreased considerably. in volume and. has minute air cells or bubbles distributed throughout and that thecomposition. is now of a creamy consistency. The mixture can be agitatedv or beaten for a period somewhat lo t fifteen minutes if this is necessary o obtain the desire consistency and degree of aeration, but thev agitating or beating should be stopped before the air cellsv or bubbles begin. to break down.

The plaster I2 shown in the photographic reproductions of Figs. 3 to 6, inclusive', represents a set plaster which has been produced in the manner above explained and applied directly. to. the metal-lath Il. This plaster contains the above;- mentioned minute cells or air bubbles which. are

distributed. throughout the plaster from the front to the back thereof and which serve to entrati and dissipate sound waves or vibrations andalso retard the transfer of heat. The ability of ourJ plaster to absorb sound is. materially increased by the surface Astippling thereofand particu- `larly by the formation of the pasfsages orchanfnels IIa. in the plaster by the nail stippling operation, The holes l1 at the outer ends ofthese passages or channels remain open and' readily 'admt the sound waves or vibrations. Since the noise reduction coeiiicient of conventional plaster.

A wall or ceiling to which our acoustical plaster has been applied can be left inthe condition obtained by. the above-mentioned brush and nail stippling or, if desired, the. stippled surface can be painted to further improve-its appearance or to obtain certain color effects. When paint is applied to our stippled plaster, it-should be applied by spraying and, although various'kinds of paints can be used, we prefer a cold-water or casein paint.

As. indicated above. our improved plaster can be applied to backing material other than a retlculated backing' as represented by the metal vlatki l l. Forexamplc, it may be applied to plain or imperforate backings formed of poured concrete,v concrete block, cinder block, old painted plastersurfaces, gypsum lath, insulating board, clay tile. gypsum tile, or brick and to backings vformed' of various other materials. In applying our acoustical plaster to theV otherv backings just n Figs. 7 and 8 we show our improved cellular plaster I8 applied to an imperforate backing I9 to provide a, steactin'e having good sound-absorbing and hse-mlmfmand which is usable for ceilings bu y suitable for side walls. In this case the backing' I9 is poured concrete the face of which has been treated or covered with a thin coat 20 formed of calcinedgypsum plaster and water or any ofthe other cementitious materials mentioned above. The coating or layer I8 of our improved plaster may be approximately one-fourth of an inch thick and may be applied over the coat 20 by the usual hawk and trowel operations. l

Thesurface of the plaster 4layer I8 ix'1-Fig.7 can be roughened, as bythe stippling herein disclosed, or can `be :troweled smooth and -can thereto'. As shown in Fig. 8, a'nish coat or layer 2I about an eighth of an inch thick of conventional flnishing lime can be applied over our improved plaster I8. The coat 2| can be troweled smooth and paint or wallpaper can be applied thereto, The plaster used in the layer I8 of Figs. .'l and 8 can be according to the example given above, jbut we prefer to decrease the specified amount of asbestos ber to 3% by Weight or thereabouts, particularly where a high degree of workability of the plaster is not required such as when the composition is to be applied to a side wall structure. In the structures of Figs. 7 and 8 the 'plaster layer I8 is of the cellular character `above described for our improved plaster and has .the minute cells dispersed throughout the same from front to back thereof andhas good sound-absorbing and heat-insulating characteristics. f

FreinY the drawings and the foregoing descrip- 'tion it will be readily understood that we have provided an acoustical plaster which, by reason of its cellular or porous nature and other characteristics, provides aneiilcient sound-absorbing medium for use on walls or ceilings. It will also Vbe understood that our acoustical plaster can be economically produced and prepared and can be applied :directly to tal lath or other backing by ordinary troweires'.' The cellular nature o f our improved plaster and the fibrous binder# embodied therein render our plaster more exible thanconventional gypsum plaster and .lssfdikely to crack as the result of movements-or vibrations of the building. --Because of its resistance to cracking our plaster can be applied in a relatively thinner layer and the weight of material needed to plaster a given area will be much less than if conventional plaster were used. In :the foregoing detailed description it will be noted that we have emphasized the high sound-absorbing capacity of our novel acoustical plaster and .have purposely employedV the term .sound-absorbing Vto distinguish from those acoustical plasters which retard sound transmission but have" only a low sound-absorbing quality. `f

Number -75 Y Having thus described our invention, we claim:

1. The method of making a plastered soundabsorbing Wall or structure of the character described which comprises,forming a plastic plaster of a creamy consistency and good workability by mixing hydrated limein a major proportion of the solid content of said plastic plaster, a brous nller and sodium sulphate of technical lauryl alcohol as a foaming agent in minor proportions of said solid content and water, aerating the mixture by mechanical agitation for approximately fifteen minutesto form and distribute minute hollow bubble cells throughout the plastic plaster, and then applying the plastic plaster thus produced directly to a suitable backing as a layer by troweling and permitting said layer to become dry and set.

2. A wall and ceiling material in the form of a dry mix composition which upon mixing with water and aeration bymechanical agitation produces a homogenous plastic plaster of a creamy relation from the front to the back surface there-V of and providing good sound-absorbing and sound-deadening characteristics, said dry mix consisting of hydrated lime in a major proportion, a fibrous ller in a minor proportion, and sodium sulphate of technical lauryl alcohol in a minor proportion as a foaming agent and-in an amount to produce said bubble cells during said mixing and aeration by mechanical agitation, said foaming agent being stable in said dry mix so as to permit storage of the dry mix or shipment thereof to a desired point of use without appreciable deterioration.

VRALPH L. DICKEY.

L CI-IES'IER R. AUSTIN. ARNOLD E. PAVLISH.

vREFERENCES CITED '-2 The following references are of record in the le of this patent: I V

' UNITED'STATES PATENTS f.; Name 'Date' `luclrer `Dec. 15,-'1891 Pfleumer Aug.'24, 1909 "Sabine Sept. 12, 1916 Hay s Sept. 25,1917 Comerma Nov. 16, 1920 Ferguson July 6,'1926 Rymarczick -s Sept. 4, 1928 Nov. 18, 1930 May '12, 1931 June 21, 1932 Sabine ;"Mar. 7 1933 Apr. 25,1933 L-- Feb. 13. 1934 vJuly 31,*1934 Apr 2i, 1936 June 2, 1936 Oct."19, 1937 Scherer J u n'e 25,1940

*FOREIGN PAIEIITS y Country -.'z'. .aDate Great Britain --..;`.....`..f`l936 

